Energy transfer and nutrient cycles

Question 1

How can biomass be measured using a calorimeter?

Answer 1

A sample of dry biomass is put into the calorimeter
It’s burnt inside and it is used to heat a known volume of water
The change of temperature in the water is used to calculate the chemical energy of the dry biomass

Question 2

How can biomass be measured using dry mass?

Answer 2

The dry mass of an organism is all the water removed
To measure this the sample is put into an oven on a low temp
At regular intervals the sample is weighed, once weight no longer changes all the water is removed

Question 3

What is the gross primary production?

Answer 3

The total amount of chemical energy converted from light energy in plants in a given area

Question 4

What is respiratory loss?

Answer 4

The loss of the gpp to the environment via heat as plants respire

Question 5

What is the net primary production?

Answer 5

The energy available to the plant for growth and reproduction, also the energy available to organisms at the next stage of the food chain.

Question 6

How do you calculate the net production for consumers?

Answer 6

Using the formula N= I - (F+R)
N- net production 
I- chemical energy in food 
F- chemical energy lost in faeces and urine 
R- energy lost through respiration

Question 7

What do decomposers do?

Answer 7

Breaks down dead organic matter by releasing enzymes on them eg, bacteria and fungi

Question 8

What do detritivores do?

Answer 8

Ingest and digest dead organic matter eg, woodlice

Question 9

How can farmers simplify their food web?

Answer 9

Reducing pest numbers, chemical and biological agents (less pests= less biomass lost when they eat it)
Limiting movement, movement increases rate of respiration

Question 10

How do you work to the percentage of energy transfer?

Answer 10

% of energy transfer= energy available after transfer / energy available before transfer X100

Question 11

Describe the nitrogen cycle

Answer 11

Nitrogen fixation- rhizobium= nitrogen to ammonia (ammonium ions)
Ammonification- saprobionts= nitrogen compounds to ammonia (ammonium)
Nitrification- nitrosommas= ammonium ions to nitrites
nitrobacter= nitrites to nitrates
Dentrification- denitrifying bacteria= nitrates to nitrogen gas

Question 12

What does mycorrhizae do?

Answer 12

A fungi which infects the tree roots, it grows and increases the area where the tree can gain mineral ions.
They have a symbiotic relationship.

Question 13

Describe the phosphorus cycle

Answer 13

Weathering causes phosphate to run into water
Phosphate is absorbed into ground water or runs off into rivers or seas
The phosphate is assimilated or absorbed by plants
Passed along the food chain via ingestion and excretion
Decomposers return it to soil sediment is converted back to rock

Question 14

Describe the process of eutrophication

Answer 14

Excess mineral ions enter the water from run off
Sudden/ rapid plant growth occurs causing light to be blocked
Dead plant matter falls to floor
Increased bacteria growth
Limiting the amount of O2 dissolved into the water
Organisms die

Question 15

Name some benefits of natural fertiliser

Answer 15

(Contains organic matter)
Cheaper to produce 
Less soluble 
Slow releasing 
Varied range of nutrients 
Fewer fossil fuels

Question 16

Name some negatives of natural fertiliser

Answer 16

Messier
Harder to apply
Higher cost of transport
Can cause nutrient enrichment

Question 17

Name some benefits of using artificial fertiliser

Answer 17

(From inorganic matter)
Cheaper to buy
Cleaner and easier to apply
Lower cost of transport

Question 18

Name some negatives of using artificial fertiliser

Answer 18

Needs reapplication 
Smaller range of nutrients 
Fossil fuels 
Can be overused leading to leeching 
Doesn't support soil organisms